I have this issue on arm (armv7-neonhfv4) and amd64:
emerge: there are no ebuilds to satisfy "=x11-libs/gtk+-3.22*:3".
(dependency required by "x11-themes/mate-themes-meta-3-r2::desktop-kit" [ebuild])
(dependency required by "mate-base/mate-1.18::desktop-kit[themes]" [ebuild])
As temporary solution I disable themes in /etc/portage/package.use
mate-base/mate -themes

I am trying to install mate and I'm getting stuck on this one package, engrampa.
* Messages for package app-arch/engrampa-1.8.1-r1:
* Cannot find $EPATCH_SOURCE! Value for $EPATCH_SOURCE is:
*
* /usr/portage/app-arch/engrampa/files/engrampa-1.8.0-caja-schema-fix.patch
* ( engrampa-1.8.0-caja-schema-fix.patch )
* ERROR: app-arch/engrampa-1.8.1-r1 failed (prepare phase):
It seems to me like the problem is it cannot find a patch that does not exist. I have not a clue how I would even fix this issue and I have looked for the patch on it's own but I came up dry. I also have tried masking the caja use flag for this specfiic package and it still gives me the same result even after confirming -caja was being used. Here is the whole output of when I emerge mate : http://pastebin.com/yD98VJ9Y and here is my emerge --info '=app-arch/engrampa-1.8.1-r1' output : http://pastebin.com/MSM0DtN3
Thanks in advance.